LBZ: LBZ Shudder clunk thump thud at take off on acceleration.

[topshelfproducts]

Hey everyone, long time listener first time caller. Been looking here and other places for a while, hoping for help.

Been creeping here for a while, 2nd duramax I have owned. Here is my issue...

2007 classic 3500. Recently while chasing driveline vibration issues have replaced all ujoints with spicer, new carrier bearing etc. After shimming driveline angles to better match my lift setup most vibration is gone, however I now have a weird clunk when starting from a stop. I usually only get it when accelerating hard, not just slow creeping from a start. If I didn't just do ujoints I would describe it to feel like that. You can kinda hear it and you can feel it, like a loose chain or something is how I would describe. Once the driveline force is applied after the thunk I don't get it anymore until the next time I stop, which it seems to feel loose then as well.

I am now thinking either rear end play, or possible stretched chain in transfer case? When I put in 4wd I get no clunks or funny sounds and it engages good.

Here is a video of the play in neutral with park brake on, when the truck is in park and off there is no play.

https://www.youtube.com/watch?v=5yN3XCUJpkQ

I have had some say that it is pinion bearings, others that transmission is slipping, others that it is the yoke needing lubed, others that.....nothing definitive. Has anyone had similar issues?


Here is a 0-60m video just to keep you entertained lol.

https://www.youtube.com/watch?v=Smfz7jU8xMg

Maybe I am being overly picky or worried and this is just normal play, but it seems excessive when my passengers can feel it and give me the "yikes" look.

Any help would be greatly appreciated. Thought about doing a full rebuild on the transfer case, but would hate to waste the time and money if that didn't do the trick.

 

[TheBac]

Moved to Tcase/Axles/Driveline

I was going to say "lube the splines" but looks like you've already done that. Could it be torsion bar related?

 

[bfmine]

Driveshaft won't move in park from the load on it keeping your truck from moving. Have you tried greasing the splines where the driveshaft slides into the t-case?

 

[topshelfproducts]

I have not greased the splines, I am searching but still a bit confused. I have a 2 piece driveshaft, is there 2 splines I need to lube? And looks like everyone is using the lucas red and tacky for the money? I will tackle this afternoon and pray it helps. If anyone has a quick write up they could link me to I would appreciate it. Thanks all!

 

[bfmine]

You have to pull the driveshaft out of the transfer case. Then add grease to the INSIDE of the slip yoke ( the part that slides into the transfer case) you will see all the splines. I just goo them up pretty good and slide it back in. I always do a real light layer of grease on the outside of the slip yoke too

 

[c20elephant]

This is what GM recommends for the splines, or just find an equivalent

ACDelco 10-4063 Multi-Purpose Lubriplate Lubricant - 1 lb

Genuine GM Fluid 19257121 High Temperature Special Lubricant - 1 lb.

 

[topshelfproducts]

Thanks everyone! I ended up with lucas red and tacky which seemed to work well. I have a 2 piece driveshaft, and greased the middle section up. Also my carrier bearing was off center just a bit so I corrected that. I was going to do the splines where it goes into the transfer case, but a buddy of mine that helped swore that is lubricated by the driveshaft, is he mistaken??? I guess I am wondering if I need to pull it out and do that as well? It did have a light layer of grease or gear oil I would assume that I could feel, but not much I could see.

Regardless...IT WORKED! In fact when I tried to test it I got on it at about 20mph and broke the tires with ease which I haven't felt before, truck just feels so much more solid all around, amazing to me how much feels better. Sounds like this is something that needs to be done a couple times a year if you drive a lot, but well worth it.

 

[c20elephant]

Now all you have to do is stop driving with both feet, that little bit of both pedals being applied does have some effect when sitting at the stop light or any other time, ask me how I know. That and a few other things I did to my truck cured mine...

The grease I suggested earlier is compatible with the transfer case lube...

 

[topshelfproducts]

Now all you have to do is stop driving with both feet, that little bit of both pedals being applied does have some effect when sitting at the stop light or any other time, ask me how I know. That and a few other things I did to my truck cured mine...

The grease I suggested earlier is compatible with the transfer case lube...

I don't follow the both pedals part? When I was speaking earlier basically I was going a steady 20mph then stomped on the gas, this would normally induce the clunk but instead just immediately rolled the tires.

May I ask what else you did to yours? My leaf springs are already clamped which I have seen some guys do.